A 15-year-old girl was admitted to our hospital with severe low back pain. She had scoliosis dextra and tight hamstrings. A plain radiograph showed high-grade L5 spondylolisthesis with vertebral scalloping from the fourth lumbar to the first sacral vertebra. L5 wide laminectomy and posterior lumbar interbody fusion by iliac bone graft was performed using the Galveston method of sacral fixation and a pedicle screw system. The rod and hook system was used from T9 to the bilateral iliac wing. We added posterolateral fusion from T10 to S1 by autograft and allograft. The patient became pain free and was able to return to student life. Three years after surgery, the radiographs demonstrated good bony fusion; however, careful long-term follow-up is needed.